The car ran on an alternate map for IVA and with the first MOT approaching in the summer I got around to building an ECU map selection switch. This is meant for temporary installation - plugging into the Aux input socket on the ECU.
Design
The circuit designed to switch between the 3 possible Maps supported by the Emerald ECU. The second pole of the switch set to illuminate a LED confirmation of position.
The LED is setup to always illuminate Green, then also illuminate Blue or Red depending on the map selected - in theory this gives Orange and Turquoise. I installed a POT to allow dimming of the green to adjust the colour mix, in the end the POT probably wasn't necessary - the Blue and Red components are so strong they drown out the green anyway.
Wiring
ECU line #7b is configured as Map switch input - either open, grounded or grounded via a 1k Ohm resistor
ECU line #1 is the ground input
ECU line #8 & 9 are used to power the very low current LED draw
#8 & #9 are input pins with internal 1k pullups to 5v. I checked with Karl at Emerald and he suggested tying both together and using as outputs - it works, there is just enough current to drive the LED which only needs about 7-8ma when two colours are lit.
Assembly
Connected via IDC cable to a right angled 9 pin D-Sub plug so it doesn't encroach into the passenger footwell.
Testing
...and in one possible location, just testing the configuration for now
Switch position 'O' gives green and selects Map 3, same as unplugging the unit:
Position 'I' gives blue and selects Map 1:
Position 'II' gives red and selects Map 2:
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